Digital wireless systems, such as wireless local area networks, may exist in a number of different frequency bands and may each use a unique communication protocol. For example, cellular and GSM telephones may operate in the 700-960 MHz frequency band, PCS and UMTS may operate in the 1700-2170 MHz frequency band and WIFI may operate in the 2.4-5.8 GHz bands.
However, PCS, UMTS and WIFI are often used with different types of devices, each with a different functionality and data processing capability. Because of the different functionality, it is often necessary for service providers to provide simultaneous infrastructure access under each of the available protocols.
One complicating factor with providing simultaneous access is that access under PCS, UMTS or WIFI often occurs in an office or commercial environment. While the environment could also be out-of-doors, the environment could also involve use within a restaurant, theater or other user space. Such environments do not allow for the use of bulky antenna or antenna structure that detract from the architecture of the space.
Another complicating factor is that PCS, UMTS and WIFI use frequency bands that are not harmonically related. As such, an antenna designed for one frequency band may not work with other bands.
One prior art solution to the problem of multiple frequency bands has been to combine a sleeve and choke into a multi-band antenna. This solution involves the use of a whip antenna with a sleeve choke surrounding the base of the whip antenna. The sleeve would typically be ¼ wavelength of the target frequency while the whip would extend another ¼ wavelength above the end of the sleeve choke. Because the choke and whip are both ¼ wavelength of the target frequency, it is difficult to tune the resulting antenna to more than one frequency band where the bands are not harmonically related. Accordingly, a need exist for better antenna that operate in multiple non-harmonically related frequency bands.